Sidescan Sonar Data File Descriptions

Documentation of the sidescan sonar data format is summarized here. The sidescan data are presented in two different ways to make them available to a broader community of users. They are presented in an unmerged form and as netCDF files.


In the unmerged form, the header information and the imagery are in separate files which both have the same prefix but different suffixes. The header information is contained in files with a hdr suffix (e.g. t1f01.hdr). These are ASCII files with the following fields:

     Field 1:  Line number
     Field 2:  Year - two digits
     Field 3:  Month
     Field 4:  Day
     Field 5:  Hour
     Field 6:  Minute
     Field 7:  Second
     Field 8:  Latitude in decimal degrees
     Field 9:  Longitude in decimal degrees
     Field 10:  Heading - this is 0 if heading was not logged
     Field 11:  Uncorrected depth in meters
     Field 12:  Corrected depth in meters - corrected for variations of the
speed of sound in water.

The associated sidescan image files that go with the header files have a suffix of ".img" (ie. t1f01.img). These files are 8-bit binary raw images. There is no tagged information identifying their size, but in the "unmerged" directory there is an ASCII file titled "filesize.txt" that summarizes the number of lines (NL) and samples (NS) in each file along with start and end time of each file.


The second data form is the netCDF file form that is compatible with the USGS WHIPS sidescan sonar processing software (Paskevich, 1992). A description of the NetCDF format, as implemented within the WHIPS software, is included here.